This invention relates to the articles of manufacture comprising a substrate having electric storage molecules bound thereto, along with methods of use thereof.
Basic functions of a computer include information processing and storage. In typical computer systems, these arithmetic, logic. and memory operations are performed by devices that are capable of reversibly switching between two states often referred to as xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d. In most cases. such switching devices are fabricated from semiconducting devices that perform these various functions and are capable of switching between two states at a very high speed using minimum amounts of electrical energy. Thus, for example, transistors and transistor variants perform the basic switching and storage functions in computers.
Because of the huge data storage requirements of modern computers, a new, compact, low-cost, very high capacity, high speed memory configuration is needed. To reach this objective, molecular electronic switches, wires, microsensors for chemical analysis, and opto-electronic components for use in optical computing have been pursued. The principal advantages of using molecules in these applications are high component density (upwards of 1010 bits per square centimeter), increased response speeds, and high energy efficiency.
A variety of approaches have been proposed for molecular-based memory devices. While these approaches generally employ molecular architectures that can be switched between two different states, all of the approaches described to date have intrinsic limitations making their uses in computational devices difficult or impractical.
For example, such approaches to the production of molecular memories have involved photochromic dyes, electrochromic dyes, redox dyes, and molecular machines, all having fundamental limitations that have precluded their application as viable memory elements. These molecular architectures are typically limited by reading/writing constraints. Furthermore, even in cases where the effective molecular bistability is obtained, the requirement for photochemical reading restricts the device architecture to a 2-dimensional thin film. The achievable memory density of such a film is unlikely to exceed 1010 bits/cm2. Such limitations greatly diminish the appeal of these devices as viable molecular memory elements.
The present invention provides a polymer comprising or consisting of a plurality of covalently joined monomeric units, the monomeric units comprising sandwich coordination compounds. The covalently joined monomeric units in the polymer may be the same sandwich coordination compounds (e.g., the polymer is a homopolymer) or different sandwich coordination compounds (e.g., the polymer is a copolymer). The polymers may be covalently bound (direct or through a linker) or noncovalently bound (via ionic linkage or non-ionic xe2x80x9cbondingxe2x80x9d, etc.) to a substrate (a carrier substrate) to produce an article of manufacture. The substrate may be any of a variety of materials, including conductors, semiconductors, insulators, and composites thereof. Particular materials include metals, metal oxides, organic polymers, etc. The polymers may be bonded singly or co-deposited with one or more other polymers and/or other information storage molecules.
Such articles of manufacture are useful for a variety of purposes. For example, these polymers and articles of manufacture afford promising electrochromic display materials, potentially offering high contrast and a wide variety of colors by tuning the applied electric potential. These materials also find potential applications as intrinsic molecular semiconductors. The rich electrochemical properties of these materials also make them useful as potential battery materials and for applications in molecular-based information storage devices.
Polymers of the present invention may be represented by Formula I:
X1"Parenopenst"Xm+1)mxe2x80x83xe2x80x83(I)
wherein:
m is at least 1 (e.g., 1, 2, or 3 to 10, 20, 50 or 100 or more) and
X1 through Xm+1 are sandwich coordination compounds (each of which may be the same or different).
Specific examples of polymers of Formula I are polymers of Formula II:
X1-Y1-X2-Y2-X3-Y3-X4-Y4-X5-Y5-X6-Y6-X7-Y7-X8-Y8-X9-Y9-X10xe2x80x83xe2x80x83(II)
wherein:
X1 through X10 are each independently selected sandwich coordination compounds;
Y1 through Y9 are independently selected linking groups or linkers; and
X3 through X10 (and Y3 through Y9) may each independently or consecutively be present or absent (e.g., to provide a polymer of anywhere from 2 to 10 sandwich coordination compounds).
Articles of manufacture of the present invention may be represented by Formula III:
A-X1"Parenopenst"Xm+1)mxe2x80x83xe2x80x83(III)
wherein:
A is a substrate (e.g., a conductor. a semiconductor, an insulator, or a composite thereof);
m is at least 1 (e.g., 1, 2, or 3 to 10, 20, 50 or 100 or more); and
X1 through Xm+1 are sandwich coordination compounds (each of which may be the same or different).
Specific examples of articles of manufacture of Formula IIII are articles of Formula IV:
A-X1-Y1-X2-Y2-X3-Y3-X4-Y4-X5-Y5-X6-Y6-X7-Y7-X8-Y8-X9-Y9-X10xe2x80x83xe2x80x83(IV)
wherein:
A is a substrate (e.g., a conductor, a semiconductor, an insulator, or a composite thereof);
X1 through X10 are each independently selected sandwich coordination compounds;
Y1 through Y9 are independently selected linking groups or linkers; and
X3 through X10 (and Y3 through Y9) may each independently or consecutively be present or absent (e.g., to provide a polymer of anywhere from 2 to 10 sandwich coordination compounds).
Particular examples of sandwich coordination compounds that may be used to carry out the present invention have the Formula XI (for double-decker sandwich compounds) or Formula XII (for triple-decker sandwich compounds): 
wherein:
M1 and M2 (when present) are metals independently selected from the group consisting of metals of the lanthanide series (Ln=La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, as well as Y, Zr, Hf, and Bi, and in the actinide series Th and U (radioactive elements such as Pm are generally less preferred);
L1, L2 and L3 (when present) are independently selected ligands (e.g., porphyrinic macrocycles); and
Q1, Q2 and Q3 may be present or absent and when present are independently selected linkers (the linker preferably including a protected or unprotected reactive group such as thio, seleno or telluro group). Preferably, at least one of Q1, Q2, and Q3 is present.
In one particular embodiment, this invention provides an apparatus for storing data (e.g., a xe2x80x9cstorage cellxe2x80x9d). The storage cell includes a fixed electrode electrically coupled to a xe2x80x9cstorage mediumxe2x80x9d comprising a polymer as described above, the polymer having a plurality of different and distinguishable oxidation states where data is stored in the (preferably non-neutral) oxidation states by the addition or withdrawal of one or more electrons from said storage medium via the electrically coupled electrode.
In preferred storage cells, the storage medium stores data at a density of at least one bit, and preferably at a density of at least 2 bits. Thus, preferred storage media have at least 2, and preferably at least 4, 8 or 10 or more different and distinguishable oxidation states. In particularly preferred embodiments, the bits are all stored in non-neutral oxidation states. In a most preferred embodiment, the different and distinguishable oxidation states of the storage medium can be set by a voltage difference no greater than about 5 volts, more preferably no greater than about 2 volts, and most preferably no greater than about 1 volt.
The storage medium is electrically coupled to the electrode(s) by any of a number of convenient methods including, but not limited to, covalent linkage (direct or through a linker), ionic linkage, non-ionic xe2x80x9cbondingxe2x80x9d, simple juxtaposition/apposition of the storage medium to the electrode(s), or simple proximity to the electrode(s) such that electron tunneling between the medium and the electrode(s) can occur. The storage medium can contain or be juxtaposed to or layered with one or more dielectric material(s). Preferred dielectric materials are imbedded with counterions (e.g. Nafion(copyright) fluoropolymer). The storage cells of this invention are fully amenable to encapsulation (or other packaging) and can be provided in a number of forms including, but not limited to, an integrated circuit or as a component of an integrated circuit, a non-encapsulated xe2x80x9cchipxe2x80x9d, etc. In some embodiments, the storage medium is electronically coupled to a second electrode that is a reference electrode. In certain preferred embodiments, the storage medium is present in a single plane in the device. The apparatus of this invention can include the storage medium present at a multiplicity of storage locations, and in certain configurations, each storage location and associated electrode(s) forms a separate storage cell. The storage medium may be present on a single plane in the device (in a two dimensional or sheet-like device) or on multiple planes in the device (in a three-dimensional device). Virtually any number (e.g., 16, 32, 64, 128, 512, 1024, 4096, etc.) of storage locations and storage cells can be provided in the device. Each storage location can be addressed by a single electrode or by two or more electrodes. In other embodiments, a single electrode can address multiple storage locations and/or multiple storage cells.
In preferred embodiments, one or more of the electrode(s) is connected to a voltage source (e.g. output of an integrated circuit, power supply, potentiostat, microprocessor (CPU), etc.) that can provide a voltage/signal for writing, reading, or refreshing the storage cell(s). One or more of the electrode(s) is preferably connected to a device (e.g., a voltammetric device, an amperometric device, a potentiometric device, etc.) to read the oxidation state of said storage medium. In particularly preferred embodiments, the device is a sinusoidal voltammeter. Various signal processing methods can be provided to facilitate readout in the time domain or in the frequency domain. Thus, in some embodiments, the readout device provides a Fourier transform (or other frequency analysis) of the output signal from said electrode. In certain preferred embodiments, the device refreshes the oxidation state of said storage medium after reading said oxidation state.
Particularly preferred methods and/or devices of this invention utilize a xe2x80x9cfixedxe2x80x9d electrode. Thus, in one embodiment, methods and/or devices in which the electrode(s) are moveable (e.g. one or more electrodes is a xe2x80x9crecording headxe2x80x9d, the tip of a scanning tunneling microscope (STM), the tip of an atomic force microscope (AFM), or other forms in which the electrode is movable with respect to the storage medium) are excluded. Similarly in certain embodiments, methods and/or devices and/or storage media, in which the storage molecules are responsive to light and/or in which the oxidation state of a storage molecule is set by exposure to light are excluded.
In another embodiment, this invention provides an information storage medium. The information storage medium can be used to assemble storage cells and/or the various memory devices described herein. In a preferred embodiment the storage medium comprises one or more different storage molecules. When different species of storage molecule are present, the oxidation state(s) of each species is preferably different from and distinguishable from the oxidation state(s) of the other species of storage molecule comprising the storage medium.
This invention also provides methods of storing data. The methods involve i) providing an apparatus, e.g., comprising one or more storage cells as described herein, and ii) applying a voltage to the electrode at sufficient current to set an oxidation state of said storage medium (the storage medium comprising one or more storage cells). In preferred embodiments, the voltage range is less than about 5 volts, more preferably less than about 2 volts, and most preferably less than about 1 or less than about 0.5 volts. The voltage can be the output of any convenient voltage source (e.g. output of an integrated circuit, power supply, logic gate, potentiostat, microprocessor (CPU), etc.) that can provide a voltage/signal for writing, reading, or refreshing the storage cell(s).
The method can further involve detecting the oxidation state of the storage medium and thereby reading out the data stored therein. The detection (read) can optionally involve refreshing the oxidation state of the storage medium. The read (detecting) can involve analyzing a readout signal in the time or frequency domain and can thus involve performing a Fourier transform on the readout signal. The detection can be by any of a variety of methods including, but not limited to a voltammetric method.
This invention additionally provides the memory devices of this invention (e.g. memory cells) in a computer system. In addition computer systems utilizing the memory devices of this invention are provided. Preferred computer systems include a central processing unit, a display, a selector device, and a memory device comprising the storage devices (e.g. storage cells) of this invention.